The disclosure generally relates to a method and apparatus for determining operational status of a coil, and more specifically, to a fault detection method and apparatus for evaluating fuel injectors having an injector coil based on signals obtained during the operations thereof.
An internal combustion engine employs various numbers of fuel injectors for supplying fuels. Electronic fuel injectors are the most commonly used fuel injectors for non-diesel engines. An electronic fuel injector may include a plurality of electromagnetically actuated fuel injection valves that are sequentially charged with a determinable quantity of fuel during a fuel metering interval and which during a subsequent interval are caused to inject fuel into the engine.
FIG. 1 is an exemplary circuit for controlling the operation of a fuel injector. An injector coil 10, such as a solenoid coil, is disposed associating with each injection valve, and is used to control the opening/closing thereof. The injector coil 10 is coupled to a voltage source 12 on one end and to a switch 14 on the other end. The switch 14 controls the coupling of the injector coil 10 to the ground. The on/off of the switch is controlled by a controller or processor, such as a PCM (powertrain control module), ECU (electronic control unit), or ECM (electronic control module).
The injector coil 10 is controlled in such a way to cause the injector coil to activate or pull in a movable member, such as a pintle, that is disposed on the injection valves. When the switch 14 is closed, a current flows through the injector coil. The current energizes the injector coil, or, produces a magnetic field, that activates the pintle on one of the injection valves to allow fuel to be injected through a valve opening into the combustion chamber of a cylinder. When switch 14 is open, no current flows through the injector coil 10. The pintle thus returns to its original position and closes the injector valve.
There is a need to evaluate the health of the injectors. There is another need to detect faulty injectors automatically. There is also a need for an easy and convenient process to determine the operation of fuel injectors without using cumbersome current probes.
This disclosure describes a method and apparatus for conveniently diagnosing fuel injectors having an injector coil and a power source that charges the injector coil during an energizing period. An exemplary tester monitors signals from the fuel injectors. The tester diagnoses the fuel injectors based on the monitored signals. The tester includes a data port for receiving signals, a data storage device, and a data processing unit coupled to the data port and the data storage device. The data storage device bears instructions to cause the tester upon execution of the instructions by the data processing unit to receive a first signal representing a first energizing state of the injector coil during the energizing period and a second signal representing a second energizing state of the injector coil during the energizing period. The data processing unit then determines a first operational status of the injector based on a level difference between the first energizing state and the second energizing state.
In one aspect, the first and second signals represent voltages of the injector coil during a period that the voltage source sends current to the injector coil. The signals may be obtained before or during the conduction of the diagnosis of the injector. The signals may be stored in the data storage device and accessible by the data processing unit. The data processing unit calculates a difference between the first and second signal, and determines whether the difference falls between a predetermined range. If the difference is outside the predetermined range, the tester indicates that the injector coil has a high resistance.
Optionally, the tester may be further configured to determine a second operational status of the injector based on levels of at least one of the first energizing state and the second energizing state. For instance, the data processing unit may access data representing injector voltages obtained during the time that the voltage source sends current to the injector coil, and determines whether the injector voltage is lower than a threshold voltage, for example, a voltage near zero volt. If the injector voltage is higher than the threshold voltage, the tester indicates that the injector coil having an unacceptable resistance. For example, the tester may indicate the injector coil as shorted or partially shorted.